1. Field of the Invention
The present invention generally relates to video display control methods, video display control systems, and apparatuses employed in such systems, and more particularly to a video display control method and a video display control system that control a camera from a remote location via a network and transmit video captured by the camera via the network to display the captured video, and an apparatus employed in such a system.
2. Description of the Related Art
Recently, the communication network environment has been shifting from circuit switching to an IP (internet protocol) network, which also requires video communication to be performed via the IP network. Video transmission as well as camera control is performed via a relatively low-speed IP network also in a video monitoring system that performs the camera control from a remote location. In this case, in order to perform the camera control accurately, it is necessary to quickly present a user with video obtained as a result of the camera control.
Compressed video still has a relatively large amount of data. Therefore, in the low-speed network, the amount of data to be transmitted becomes large for the network bandwidth, and a delay is prone to be caused in the data transmission. As a result, a response to the camera control is delayed, thus resulting in poor camera operability.
FIG. 1 shows an operation sequence of a conventional video display control method. In the drawing, when a control apparatus 1 performs operation control such as PAN, TILT, or ZOOM, the command signal is transmitted to a controlled apparatus 2 via a network. Propagation delay of a command (ex. 50 ms), a video encoding time (ex. 100 ms), and a delay in a transmission of compressed video data (ex. 50 ms) sums up to approximately 200 ms. Further, video transmission requires another 1,000 ms. Therefore, it takes approximately 1,200 ms before the control apparatus 1 obtains the video. This case is based on a transmission rate of, for instance, 100 Kbps, and if the transmission rate is 25 kbps, the delay is approximately 4 seconds.
Conventionally, response to a control command has been improved by reducing the amount of data to be transmitted by increasing a video compression rate or reducing a screen size. This, however, does not drastically improve the response, but has a disadvantage of causing deterioration in video quality.